It's also relatively easy to justify, though. Let me take a crack at it. Before I begin, let me state as a disclaimer that I do not agree with the actions taken by the Leipzig profprofessors, and only seek to try to understand their reasoning.
These students, these male students come from a society where rape is prevalent to the point where it seems almost encouraged. And while it's true that most Indian males likely don't rape people, one has to consider that the probprobability of the student you bring in being one of these males is higher than zero, and potentially even significant. Do you really want to take that chance, especially when by bringing in this student you're attaching your reputation to them?
tl;dr not all m&ms are poisoned